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If it is salt instead of coolant & the exhaust manifold is salt water cooled, the manifold may be leaking salt water into the ports? If you are not losing any coolant the only other source I can think of is salt water in the fuel that is getting past the filter/separator? That may be a stretch, however. It would be interesting to know what you find.

Paul T
 

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Many thanks to those who have responded with suggestions.

An update:

We went on across Biscay. We had the right weather and crew was available, so we changed the oil and did the crossing. I thought I could get it fixed in NW Spain, La Coruna. Mechanic there said he didn't have time and referred us to the regional distributor in Vigo further south.

On arrival in Vigo several days later the Yanmar service supervisor and his mechanic were aboard and did a 45 minute very thorough visual inspection of the engine. They looked at the oil on dipstick and did swipes of oil on the top of the valve cover. They could find nothing wrong with the oil, and no indicaton of oil in the coolant. (Recall the French mechanic called the oil "beautiful", these guys felt the same way). They aid there was no (visual) sign that any liquids were in the oil. They traced the cooling system looking for leaks and found none. Their conclusion: there was nothing wrong with the oil, the coolant or the engine. I got the sense that if they were from NJ they'd have said, "Fuggetaboudit"!

"But what about the lab reports", I countered. They took copies and said they would send their write up (I have a copy) and the reports to the Netherlands Yanmar European HQ for comments/suggestions. I've heard nothing so far.

So, we continue on our path south and are planning on changing the oil every 40-50 hrs and continuing the lab tests.

I've started a very close monitoring of the coolant levels and for the last four times we've operated the engine I've seen virtually no drop in the coolant bottle (maybe a 1/6th inch--about the thickness of the mark I made on the bottle.

I have all the parts we need to do a complete tear down of the block, but I can't seem to find a Yanmar mechanic who wants to take my money. We'll keep trying as we move south. We have a 10 day stop in Lagos in southern Portugal and perhaps we will have word from HQ gurus by then.

If we were in the US near the guys who installed the engine and had access to all the high tech tools/methods described in some of the posts above I'm sure with time and money we could nail this problem down, but for now, the realities of long distance cruising in foreign lands prevail and we just have to keep moving so we're positioned in November for the trade winds crossing.

I've had a couple of ideas that you might comment on:

1/ the engine is turbocharged and has an air cooler (seawater cooled). A small leak there could put small quantities of seawater in the intake air. The water would be vaporized in combustion and salts left on cylinder walls to find their way eventually to the oil.

2/ the rough seas we sometimes experience could be sloshing water from the muffler up the elbow. I doubt this as the installation team at NEB Portsmouth are very professional and I doubt they would not have engineered the exhaust system correctly.

3/ I wondering if my operating methods have contributed....we have a Gori prop (with overdrive) that allows us, when motoring in flat seas, to reach near hull speed at 2200 rpm (vs say 2800-2900 with the normal pitch). I've used the overdrive a lot (when fuel is $8 / gal one looks for savings where you can find them). The lower rpm reduces the pressure in the exhaust system and may allow a larger quantity of water to remain in the muffler when the engine shuts down. Follow that with sailing in heavy swell / rough seas (with engine off) and we may get the sloshing up into and beyond the elbow????

Will continue with updates when available.

Thanks again for the help thus far.
Kind of lost track of the details. Did the lab verify that it is salt & not coolant in the oil? If so, I think your item #1 could be it? Is there any evidence of salt or corrosion in/on the turbo intake blades?

Paul T
 

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Trying to picture a graph of that, it seems like a large increase from 85 to 215 hrs., more than twice the slope of from 63 to 85. Maybe that's a clue. Is there a normal sodium content of new oil? Is there an acceptable level?
Interesting, if I am doing the math correctly, it looks something like this:

1. 4 ppm per hour

2. 24.2 ppm per hour

3. 9.8 ppm per hour

Right, how much is too much?

If there is no water in the separators it appears that some sea water may be coming back through the exhaust manifold system. I would think you would have to have a whole lot of salt water in the fuel for any unburned fuel to contaminate the oil. Don't know much about oil additives, but if they are causing the readings, I would think the readings would be more consistent?

Maybe raising the loop in the exhaust riser, if possible, would help prevent any back flow, if there is any? Or, if possible, install a drain valve in the bottom of the muffler? Maybe a rubber "Flapper" valve/plate over the exhaust outlet?

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UPDATE:

When we arrived in Lagos, Portugal I invited yet another Yanmar mechanic aboard for a consult and another oil analysis in a local lab, results of which aren't back yet.

Since the last oil change I've stopped using the Gori overdrive and have been tracking the coolant level religiously.....in 50 hrs we're down only 1-2mm in the overflow bottle. The mechanic says that's not unusual.

Conclusion: it's not a coolant leak.

If it isn't coolant, it's got to be seawater. There are three sources of seawater: the oil cooler, the air cooler and the exhaust system. We tested the oil cooler and it's good. That leaves two possibilities.

The mechanic in Lagos took a hard look at the exhaust system and he thinks the problem may lie there. I have since done an analysis of the volumes of the hose runs and the muffler and have reached the conclusion that he's probably spot on.

When the new engine was installed it required that we increase the size of the exhaust lines from 2.5 to 3 inch hoses. The larger hose was stiffer and required installation of hard fiberglass elbows in a couple of places where the turns were tight. With those exceptions, the general layout of the old exhaust system was followed in terms of the hose runs.

Exiting the exhaust elbow we now have a 90 deg elbow and then 20" of hose to the water lift muffler (side in, top out). We have a 28" vertical rise coming out of the muffler to a 90 deg elbow and then a 5+ ft horizontal run aft to the steering compartment where the hose loops up to the top of the space and then drops to the exhaust port on the transom. In all, there is probably 9-10 feet of hose between the top of the muffler and the highest point in the exhaust hose run plus the ~ 2 feet between the exhaust elbow and the muffler.

The new engine was actually smaller than the old one (despite the ~2x HP) and so the height differential between the exhaust manifold and the muffler has decreased by a few inches, and due to the new 3" very stiff hose we need for a 90 deg. elbow immediately below the exhaust elbow -- all of which means that the angle of the hose running to the muffler is much shallower than with the old engine. My estimate is that it's a 8-10" drop from the exhaust manifold to where the hose enters the muffler, and that the hose is 10-15 deg off horizontal.

Less height differential + shallower angle = higher potential that we end up with seawater in the hose between the muffler and the engine IF the muffler fills with water when the engine shuts down.

Enter the new 3" hose -- larger diameter = greater volume of water in the hose and greater chance that the muffler has more water in when the engine shuts down.

Based on the calculations I've done of the volume of the hoses and the volume of the muffler, and using assumptions for the gas to water ratio in the hoses provided by Centek and Vetus tech support (Estimates range between 25 and 50%)....I've come to the conclusion that the muffler is overfilling (it should be no more than 1/2 full after shut down according to the tech guys).

Over filling the muffler puts standing water in the hose between the engine and the muffler when the engine is shut down. Now put the boat in a big following sea like we had crossing he Atlantic last summer and you now have water sloshing about in the pipe between engine and muffler with the potential for a few sloshes pushing small quantities of water up to the top of the exhaust elbow and into the exhaust manifold and from there a few drops get into the cylinders with open exhaust valves. It doesn't take a much water to register ppm of salts the oil. It's certainly not enough water to interfere with the starting of the engine. And, of course, once the engine starts the few droplets of salt water are immediately evaporated within the cylinder and hence no sign of foreign liquid in the oil.

So, the current hypothesis is the salts are from seawater entering the engine through the exhaust due to overfilling of the muffler, caused to long hose runs and larger hose.

With the approach of the fall season I need to move the boat further south and so we will not have time to address a redesign of the exhaust system before moving on from Portugal. We're moving on to Morocco next week (only 200 miles) where tech support and suitable parts are probably in short supply. We have some down time in Morocco and , my interim solution will be to install a small ball valve in lower part of the muffler which will enable me to drain the muffler into the bilge after shutting down the engine when at sea. I'm also going to install a flapper on the exhaust as a preventive measure until we sort the entire system out.

We will run with these two changes to the system and continue to change the oil every 50 hours until we can be sure that we've found the problem. My guess is that draining the muffler following every engine shut down will solve the problem....but that remains to be seen.

Stay tuned.
Sounds like your analysis is good. If, as Delta suggested, you don't have a riser out of the exhaust manifold, It wouldn't hurt to install one, even something temporary. Anytime something is changed there is always the possibility for problems. I am surprised your engine installer would put the engine in without a riser?

Not sure if I followed your description of the plumbing properly? Maybe pictures or a drawing?

Paul T

Edit: Oops, didn't see your post #63 Maybe a riser "loop" higher than the manifold somewhere in the system?
 
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